As the printing resolution of ink jet printers increases, so does the number of nozzles on the ink jet print head. For each nozzle used to eject ink to form printed pixels on the print medium, there is a corresponding heating element. As nozzles counts have increased, driver circuitry has been incorporated on the print head substrate along with the heating elements. The driver circuitry activates the heating elements in a time-multiplexed fashion, with combinations of power and address lines being used to select the heating element or elements to be activated. For example, in a 208-nozzle print head, there may be sixteen power lines and 13 address lines for a total of 29 signal lines used to activate 208 heating elements. (16.times.13=208).
In a typical ink jet printer design having a print head that scans across the print medium, each of the signal lines generally must be brought from a printer controller to the print head through a flexible cable. Also, there must be an interconnection, such as a bonding pad on the print head for each signal line that connects to the driver circuitry on the print head substrate. In a low-cost ink jet printer design, the cost of such interconnects, and the cost of print head drivers, and can be quite significant. A reduction in signal lines would simplify the design and reduce the cost of printers and print heads. Further, reducing the number of signal lines would allow more flexibility in possible design configurations.
Therefore, a heating element addressing scheme is needed that reduces the number of signals lines connecting the print head to the printer controller.